HEM_PHY
Lecture 5
BLOOD GROUPS AND THEIR
CLINICAL SIGNIFICANCE
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Why is blood needed?
Blood is needed for
• Accidents esp. MVA cases
• Transfusions in surgery
• Treatments : Leukemia, cancer,
thalassemia, haemophilia, complications
during delivery, etc.
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Desired Learning Outcomes
On completion of this topic, you should be able to
1. Explain the importance types of blood
groups and discuss its clinical importance.
2. Describe the physiology of mismatched blood
transfusion reactions
3. Explain the process of cross matching –
major and minor
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Human Blood Groups
• RBC membranes have glycoprotein antigens on
their external surfaces.
• Human erythrocytes has >300 antigenic
determinants
• These antigens are:
– unique to the individual
– promoters of agglutination and are referred to as
agglutinogens
– recognized as ‘foreign’/non-self if transfused into
another individual
• Presence or absence of these antigens is
used to classify blood groups
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Markers on RBC
• Agglutinogens = antigens
that promote agglutination
– A B O – 2 glycoprotein
antigens, A and B
– Rh
– Duffy; Kidd; Kell; Lewis
• NOTE: Agglutinogens of these
systems are usually very poor
antigens – they do not produce
antibodies against them and
reactions are relatively mild.
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i. The ABO System
 Discovered in 1901 by Dr. Karl Landsteiner
 4 main phenotypes (A, B, AB, O)
 ABO gene located on long arm of
chromosome 9.
 Antigens/agglutinogens Type A and Type B
on the surface of the RBCs are the cause of
blood transfusion reactions [BTR]
 Thus, the presence or absence of these Ag’s
is the essential basis that blood is grouped
for the purpose of transfusion.
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Landsteiner’s Law
•
•
Only applicable to the ABO system
2 laws :
(I)
1st Law: WHEN AN AGGLUTINOGEN IS PRESENT ON
THE MEMBRANE OF RBC, THE CORRESPONDING
AGGLUTININ MUST BE ABSENT IN THE PLASMA OF THE
PERSON.
Eg: RBC contains A –Ag; plasma must not contain α
agglutinin; otherwise there will be death!
2nd Law: WHEN THE RBCS IN AN INDIVIDUAL IS
DEVOID OF AGGLUTINOGEN, PLASMA SHALL CONTAIN
THE CORRESPONDING AGGLUTININ.
Eg: RBCs contain no B or A antigen. In the plasma of this
individual; there must be anti-A and anti-B agglutinins.
Therefore: “A” group blood must contain β-agglutinin in the plasma
and Group O blood must contain both α and β agglutinins in
the plasma.
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.
(ii)
ABO Group
• Blood usually has antibodies that can react with
antigens
– e.g. anti-A antibody or anti-B antibody
– Thus: type A has anti-B Ab and vice versa
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Antigens & Antibodies in the ABO system
Blood Group
Antigens on
RBCs
Antibodies in Serum
Genotypes
A
A
Anti-B
AA or AO
B
B
Anti-A
BB or BO
AB
A and B
Neither
AB
O
Neither
Anti-A and anti-B
OO
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ABO Markers
• ABO –
glycoproteins
– Which one is most
common?
– Least prevalent?
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ABO Markers
– Preformed antibodies
called agglutinins in
the plasma is unique
to the ABO blood
groups.
– Recall your Practical:
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ABO INCOMPATIBILITY
• reaction of the immune system that occurs if two different and not
compatible blood types are mixed together.
• Surface Antigens can act as immune system triggers.
• Being exposed to another type of blood can cause a reaction.
• Blood types must be matched to avoid an ABO incompatibility
reaction.
• Important when a patient needs to receive BLOOD
(TRANSFUSION) or have an ORGAN TRANSPLANT.
• Because type O lacks Ags, type O blood does not cause an
immune response.
• This is why type O blood cells can be given to patients of any
blood type. People with type O blood are called "universal
donors."
• However, people with type O can only receive type O blood.
• Since antibodies are in the liquid part of blood (plasma), both
blood and plasma transfusions must be matched to avoid an
immune reaction.
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ii. THE Rh SYSTEM
– Discovered by Landsteiner & Wiener in 1937
– Antigen discovered in the Rhesus monkey
– Rh is an Ag on the RBC
•
•
•
•
a. Rh+ has the Ag (85% of the population)
b. Rh- does NOT have the Rh antigens
c. Rh+ can accept Rh+ or Rh- blood
d. Rh- can accept ONLY Rh- blood
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Inheritance of ABO & RH
 ABO & RH genes are not linked
 ABO & Rh(D) type are inherited
independently.
 Quiz:
Can an A Rh(D)+ mother and a B Rh(D)+
father have an O Rh(D) neg child?
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Inheritance of ABO and Rh(D)
Mother
Father
Group A AO
Group B
BO
Rh(D) + Dd
Rh(D) + Dd
Group A AO
Group B BO
Group O OO
Rh(D) pos Dd
Rh(D) pos Dd
Rh(D) neg dd
Ans:
Yes, An A Rh(D)+ mother and a B Rh(D)+ father
can have an O Rh(D) neg child.
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Rh Factor
• There are 45 different types of Rh
agglutinogens.
– Common : C, D, and E
• ~ 85% of Americans are Rh positive, carrying
the D antigen.
• Presence of the Rh agglutinogens on RBCs is
indicated as Rh+
• As a rule, a person’s ABO and Rh blood
groups are reported together, for example,
O+, A-, and so on.
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Rh Antigens
• D antigen is the most common and most
immunogenic
• Approximately 80-85% Caucasians have D
antigen
• Individuals lacking this allele are called “Rhnegative”
• Only develop antibodies against the D
antigen after exposure
(transfusion/pregnancy)
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Rh antibodies
• IgG class of immunoglobulins
• Lack capacity to bind complements
Hemolysis does not occur after 1st transfusion
with Rh factor but it occurs in later
transfusions.
Why?
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Significance of Rh(D)
80% of Rh(D) negv persons exposed to Rh(D)
positive blood will develop anti-D.
Anti-D can also be stimulated by pregnancy with
an Rh(D) positive baby
Sensitisation can be prevented by the use of
anti-D immunoglobulin, antenatally and post
natally
Rh(D) neg females of childbearing potential
should never be given Rh(D) positive blood
products
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Rh AND THE PREGNANT WOMAN
• Transplacental passage of D-positive fetal RBC’s into
D-negative mother produces anti-D (IgG)
• Anti-D IgG traverses the placenta and coats fetal
RBC’S leading to extravascular hemolysis
• Clinically manifests as hemolytic disease of the fetus
and newborn
- anemia, hepatosplenomegaly, hydrops fetalis, and death!
Background
Hydrops fetalis (fetal hydrops) : a serious fetal condition defined as abnormal
accumulation of fluid in 2 or more fetal compartments, including ascites,
pleural effusion, pericardial effusion, and skin edema.
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Rh Incompatibility
– Antibodies against the Rh+ factor develop in Rhperson after the first exposure from transfusion.
– A clinical problem - if they receive 2nd transfusion of Rh+
blood - Rh Ab will agglutinate with the Rh Ag Rh- mother and
Rh+ father can also develop Rh problems with having children.
If the mother has a baby that is Rh+, her body will develop
antibodies to the Rh antigen so that a second pregnancy
with a Rh+ baby will result in the mother’s antibodies
attacking the unborn child’s RBCs.
Ans: [HDN, or Erythroblastosis fetalis]
• Prevention : A shot of RhIg @ RhoGam™ is given shortly
after birth to block the development of antibodies.
• Symptoms of transfusion reaction: chills and fever, rash,
itching, SOB, nausea, nephralgia, hematuria, shock and
death.
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Erythoblastosis fetalis @ HDN
 Disease of fetuses and newborn infants
• In transfusions, Rh system is 2nd important to ABO system.
• Rh incompatibility most common & severe cause of HDN.
 Can happen when an Rh-negative woman and an Rh+ man
produce an Rh+ baby. The baby has inherited the Rh+ Ag from
the Father, and the Mother has developed anti-Rh Ab in
response to the Ag.
• Most Rh-negative people who receive Rh+ blood will develop
anti-D Ab. A later transfusion of Rh-positive blood could
result in a severe or fatal transfusion reaction.
 These Ab [agglutinins] can diffuse through the placenta into the
fetal circulation and cause RBC agglutination.
 enter the mother's bloodstream, causing the mother to make
anti-D antibodies.
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Erythoblastosis fetalis @ HDN….
• Unlike ABO Ab’s, the structure of anti-D Ab makes it
possible to cross the placenta and enter the baby's
bloodstream.
• Specifically, the mother's anti-Rh+ antibodies agglutinate
her infant's Rh+ blood.
• Symptoms include life threatening anemia, jaundice, fever,
swollen tissues from edema, and an enlarged liver and
spleen.
• Serious cases of this condition are treated by fetal blood
replacement.
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Preventing Erythroblastosis Foetalis
@ HDN
First step: Find out the Rh types of the expectant parents.
• If mother is Rh-negative and father is Rh-positive, baby is at
risk for developing HDN.
The next step: Mother's serum is tested to make sure she doesn't
already have anti-D Ab from a previous pregnancy or
transfusion; similar to blood typing.
Finally, the Rh-negative mother is given an injection of Rh
Immunoglobulin (RhIg)/ RhoGam™ at 28 weeks of gestation
and again after delivery, if the baby is Rh+.
The RhIg will attach to any Rh+ cells from the baby in the mother's
bloodstream, thus preventing them from triggering anti-D Ab
production in the mother.
The Rh- woman should also receive RhIg following a miscarriage,
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abortion, or ectopic pregnancy.
• RhoGAM
– Injection of anti-Rh antibodies given soon after
every delivery, miscarriage, abortion-binds
– Inactivates fetal Rh antigens so mother’s
immune system doesn’t respond
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Complications in Blood
Transfusions
Allergic reaction,
Air embolism,
Citrate intoxication,
Hypothermia,
Hyperkalemia,
Hemosiderosis,
Mismatched transfusion.
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Transfusions
• If mismatched blood given antibodies bind to it and
hemolyze cells
• Type AB has no AB antibodies so can receive any ABO
type blood called Universal recipients
• Type O have neither antigen so can donate to any other
ABO type called Universal donors
• Misleading: because of many other blood groups
must be matched also.
• Other blood groups: example:
• Duffy-negative blood occurs much more frequently in people of
African origin
• hh antigen system (also known as the Bombay blood group)
individuals who can only receive blood safely from other hh
donors, because they form antibodies against the H substance
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Transfusion Reactions…
• Transfusion reactions require
– immediate recognition,
– laboratory investigation, and
– clinical management.
• If a transfusion reaction is suspected during blood
administration, the safest practice is to stop the
transfusion and keep the intravenous line open with
0.9% sodium chloride (normal saline).
Check of the information on the blood unit label and the
patient's identification should be performed to ensure that
the "right" blood unit was administered to the "right"
patient.
In most cases, the residual contents of the blood component
container should be returned the blood bank, together with
a freshly collected blood sample from the patient, and a
transfusion reaction investigation should be initiated.
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Transfusion Reactions
• During or within 24 hours of a
blood transfusion;
Acute transfusion reactions
present as adverse signs or
symptoms; reactions include
fever, chills, pruritus, or
urticaria.
Other signs include
• severe shortness of breath,
• red urine (see pic),
• high fever, or
• loss of consciousness [may
be the first indication of a
more severe potentially fatal
reaction].
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Agglutination
Unagglutinated blood smear
•
•
•
•
•
•
Agglutinated blood
When different types of blood are mixed within the body, the reaction can be
a hemolysis as well as agglutination.
Depending on the blood types of the donor and the recipient, mismatching
can result in death or no problems at all.
Different types of blood are recognized on the molecular level and
sometimes rejected by being destroyed and ultimately filtered out by the
kidneys in order to expel them from the body along with urine.
In the case of a transfusion mistake, worst case scenario would be
kidney failure and death.
Why? when the kidneys try to filter the blood, they essentially become
clogged as they are overwhelmed and cease being effective filters.
Additionally, there is a rapid depletion of blood clotting factors which causes
bleeding from every body orifice.
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Compatible √
Not compatible !!
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–
–
–
–
–
–
Symptoms of ABO incompatibility
Back pain
Fever
Blood in urine
Jaundice
Feeling of ‘impending doom’
Anaphylaxis
Signs and tests of ABO incompatibility
– Bilirubin level is high
– Complete blood count (CBC) shows damaged RBCs
and probably mild anemia
– Decreased platelet count; increased fibrin
degradation
– Lab test (perhaps a repeat one) shows incompatibility
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Treatment of ABO incompatibility
• Intravenous fluids
• Drugs to raise BP if it drops too low
• Steroids & antihistamines – to treat swelling
and allergies
• Promote diuresis
• Hemodialysis for disrupted renal function
Complications of ABO incompatibility :
Immunological effects : Hemolysis, urticaria, noncariac
pulmonary edema, anaphylaxis
Non-immunological effects: Fever with shock, Kidney
failure, congestive heart failure, hypotension, death (if not
treated)
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Summary:
ABO INCOMPATIBILITY
Donor blood
+
Recipient Ab
ACTIVATES Complement System
Intravascular hemolysis
Hemoglobinemia
Hemoglobinuria
DIC
Profuse Bleeding
Acute circulatory
problem
Anuria
DEATH
One of the most lethal effect of TRANSFUSION: RENAL FAILURE
Excess Hb from the hemolised RBCs leaks through the glomerular
membranes into the renal tubules. Reabsorbtion of water from the tubules
causes Hb conc. to rise; resulting in the HB precipitation and subsequent
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blockade of the tubules.
DIC- Disseminated Intravascular Coagulation
•
DEFN: a serious disorder in which the
proteins that control blood clotting
become abnormally active.
Causes
• Normally in injury, certain proteins in the
blood become activated and travel to the
injury site to help stop bleeding.
• However, in DIC patients, these proteins
become abnormally active; due to
inflammation, infection, or cancer.
• Small blood clots clog up the vessels and
cut off blood supply to organs eg. liver,
brain, or kidney; ORGAN DAMAGE
• Over time, the clotting proteins are
consumed or "used up" ; the person is
then at risk for serious bleeding, even
from a minor injury or without injury.
• This process may also break up healthy
red blood cells.
• DIC can be life-threatening!
Risk Factors:
Blood transfusion reaction
Cancer, esp. leukemia.
Pregnancy complications (such as
placenta that is left behind after
delivery)
Recent surgery or anesthesia
Sepsis; Severe tissue injury (as in
burns and head injury)
Symptoms
Bleeding, possibly from multiple
sites in the body
Blood clots
Bruising
Drop in BP
Treatment: Blood clotting factors may be replaced with plasma transfusions. Platelet
transfusions can raise the blood count. Heparin, a medication used to prevent
clotting, is sometimes used to interrupt clotting events.
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a.k.a: Consumption coagulopathy
•http://www.nlm.nih.gov/medlineplus/ency/article/000573.htm
Cross matching – major and minor
Crossmatching is the final step in pretransfusion testing.
 Commonly referred to as compatibility testing, or "Type and Cross."

Importance of Cross matching: It is a direct and final check
to detect whether there is any mismatching btw the bloods of
potential donors and potential recipient.
• Donor’s RBCs are mixed with recipient’s serum and
examined if whether there is any agglutination or not
[MAJOR X-matching].
• Also, admix recipient’s RBCs with donor’s serum [MINOR
X-matching].
• Observe: if there is an agglutination or not.
• NO AGGLUTINATION: in either case means that the two
blood are perfectly COMPATIBLE: Transfusion is allowed.
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Cross matching …
• Before blood from a donor and the recipient are
crossmatched, both are ABO and Rh typed.
• Also, antibody screening is done to look for Ab to certain Rh,
Duffy, MNS, Kell, Kidd, and P system antigens.
• If an antibody to one of these antigens is found, only
blood without that antigen will be compatible in a
crossmatch.
• To begin the crossmatch, blood from a donor with the same
ABO and Rh type as the recipient is selected.
• In a test tube, serum from the patient is mixed with RBCs from
the donor. If agglutination/clumping occurs, the blood is not
compatible; if clumping does not occur, the blood is
compatible.
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Cross matching …
• IF TIME IS AVAILABLE for blood typing, RBCs of the
recipient type (type specific cells) are given.
• During an EMERGENCY, TIME factor may force the
initial use of O-RBCs & preferably Rh-negative.
• Why? O-blood type, the universal donor has no ABO
antigens for a patient's antibodies to attack.
• In contrast, AB blood type, the universal recipient, has
no ABO antibodies to attack the antigens on transfused
RBCs.
• In either case, the cross-match is continued, even
though the transfusion has begun; as a precaution.
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Major and Minor Cross matching of blood
Donor’s Blood
Patient’s blood
Plasma
RBCs
Patient’s Plasma + Donor’s RBCs = Major Cross-Match
Donor’s Plasma + Patient’s RBCs = Minor Cross-Match
TASK: Mix and place a drop of plasma or RBC onto slide/test tube
Observe for Agglutination or Hemolysis.
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What is Apheresis?
– The process of apheresis involves removal of whole blood from a patient or
donor. Within an instrument that is essentially designed as a centrifuge, the
components of whole blood are separated. One of the separated portions is then
withdrawn and the remaining components are retransfused into the patient or
donor.
– The components which are separated and withdrawn include:
– Plasma (plasmapheresis)
– Platelets (plateletpheresis)
– Leukocytes (leukapheresis)
During centrifugation;
blood separates into components
(P = plasma; PRP = platelet rich
plasma; WBC = leukocytes; RBC = red
blood cells)
The component to be removed can be
selected by moving the level of the
aspiration device at the right. In this
example, plasma is being removed.
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– The process of apheresis has become essential in
providing blood components for therapy.
– A volunteer donor will undergo apheresis to supply
specific components. The process takes a few hours.
– Examples include:
• Plateletpheresis: this is the most common means for supplying
HLA matched platelets to patients who have become HLA
sensitized and require platelets from a single donor whose HLA
type matches theirs.
• Plasmapheresis: the plasma can be removed to supply blood
components such as clotting factors. Donors can give plasma
via this mechanism more often than they can donate whole
blood.
• Leukapheresis: the leukocytes (specifically the granulocytes)
can be harvested from a donor to supply granulocytes to help
fight infection in patients such as neonates. In some cases of
leukemia with very high white blood cell counts, removal of the
excess leukocytes may help to prevent complications of
thrombosis.
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Thank you
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